The present invention concerns a method for dry forming a fabric. The invention also concerns an apparatus for dry forming a fabric formed of at least two non-woven fabrics.
It is prior art to dry form a fabric with one or more non-woven fabrics which are formed on a former wire or several succeeding former wires. The dry forming can only occur by using cards or former heads.
When making fabrics it is often desirable to combine non-woven fabrics with different properties, so that the finished fabric appears as an integrated product with different properties, e.g. varying density across the thickness of the combined web.
When making an integrated product formed of several non-woven fabrics with large layer thickness, an attachment problem will arise from the vacuum box disposed under a former wire. When placed several former heads are arranged in succession, the layer thickness of the last former head in a series of distributed fibre layers will be subjected to a rather small suction action, since the vacuum effect will only penetrate through the already formed fabric with difficulty. Alternatively, it will be necessary to work with differentiated suction boxes under the former wire for establishing greater and greater vacuum in the conveying direction of the former wire.
It may also be required to reduce the conveying speed of the former wire in order to achieve sufficient vacuum effect through the formed fabric. This entails a reduced efficiency for the apparatus.
By known apparatuses, where a fabric is formed by using two succeeding cards, it may also be wanted to place an intermediate non-woven fabric interposed between the two non-woven fabrics formed by the cards. However, it is difficult to establish vacuum in an area between two cards, and this means that it may be difficult to gent an airlaid gauze layer placed between two cards in an existing apparatus. Such a product consisting of carded non-woven fabrics, which are disposed at both sides of an airlaid non-woven fabric, may e.g. be suited for so-called wipe products.
It is the purpose of the invention to indicate a method and an apparatus that enable combining different non-woven fabrics and which avoid problems with need for larger vacuum by thicker layers, and which in addition are suited for use by formation of an airlaid non-woven fabric between two succeeding cards.